Possible role of neocytolysis in anemia in hemodialysis patients with darbepoetin alfa or continuous erythropoietin receptor activator

Efficacy of daprodustat on anemia in hemodialysis patients with sustained inflammation: a case report

Hypoxia-inducible factor prolyl hydroxylase inhibitors improve anemia in CKD and dialysis patients and were approved for anemia treatment with these populations in Japan. An 89 year-old man with anemia and on maintenance hemodialysis was successfully treated with a dose-up of darbepoetin alfa from 10 to 20 μg per week, and the dose was gradually tapered to 5 μg. Later, serum hemoglobin levels decreased with the newly occurring sustained inflammation and left pleural effusion of an unknown cause, and the darbepoetin alfa dose was increased again to 20 μg per week, which was not effective. Darbepoetin alfa was switched to 4 mg of daprodustat daily, which was fairly effective under sustained inflammation, with serum hemoglobin levels maintained at 11-12 g/dL. The increase in hemoglobin levels was ascribed to the increase in the number of red blood cells, not the mean corpuscular hemoglobin level. During the inflammatory state, despite the contrasting effect on anemia by the 20 μg of darbepoetin alfa weekly and 4 mg of daprodustat daily, the reticulocyte counts were equivalent. The serum erythropoietin levels during daprodustat administration were within the physiological range (8.5-18.8 mIU/mL). For anemia treatment in hemodialysis patients, daprodustat is less influenced by the inflammatory status than darbepoetin alfa, and one of the possible reasons for this includes the extended red blood cell lifespan.

Absence of neocytolysis in humans returning from a 3-week high-altitude sojourn

AIMS

Total haemoglobin mass (tot-Hb) increases during high-altitude acclimatization. Normalization of tot-Hb upon descent is thought to occur via neocytolysis, the selective destruction of newly formed erythrocytes. Because convincing experimental proof of neocytolysis is lacking, we performed a prospective study on erythrocyte survival after a stay at the Jungfraujoch Research Station (JFJRS; 3450 m).

METHODS

Newly formed erythrocytes of 12 male subjects (mean age 23.3 years) were age cohort labelled in normoxia (110 m) and during a 19-day high-altitude sojourn by ingestion of ¹³ C2- and ¹⁵ N-labelled glycine respectively. Elimination dynamics for erythrocytes produced in normoxia and at high altitude were measured by isotope ratio mass spectrometry of haem, by determining tot-Hb, reticulocyte counts, erythrocyte membrane protein 4.1a/4.1b ratio and by mathematical modelling.

RESULTS

Tot-Hb increased by 4.7% ± 2.7% at high altitude and returned to pre-altitude values within 11 days after descent. Elimination of ¹³ C- (normoxia) and ¹⁵ N- (high altitude) labelled erythrocytes was not different. Erythropoietin levels and counts of CD71-positive reticulocytes decreased rapidly after descent. The band 4.1a/4.1b ratio decreased at altitude and remained low for 3-4 days after descent and normalized slowly. There was no indication of haemolysis.

CONCLUSION

We confirm a rapid normalization of tot-Hb upon descent. Based on the lack of accelerated removal of age cohorts of erythrocytes labelled at high altitude, on patterns of changes in reticulocyte counts and of the band 4.1a/4.1b ratio and on modelling, this decrease did not occur via neocytolysis, but by a reduced rate of erythropoiesis along with normal clearance of senescent erythrocytes.